Outer Sphere Electroreduction of CCl₄ in 1-Butyl-3-methylimmidazolium Tetrafluoroborate: An Example of Solvent Specific Effect of Ionic Liquid

Abstract

Electrodics of CCl4 reduction in 1-butyl-3-methylimmidazolium tetrafluoroborate [BMIM][BF4] room temperature ionic liquid (RTIL) is reported. A convolutive analysis of the cyclic voltammograms suggests that CCl4 electroreduction follows stepwise (outer sphere) dissociative electron transfer pathway, rather than the sticky dissociative (inner sphere) electron transfer, as in the case of conventional organic solvents. This difference in the mechanism of electron transfer initiated bond cleavage is attributed to the solvent specific effects, namely, stabilization of CCl4*- intermediate radical anion in RTIL, which in turn decreases the electron transfer rate and thus the carbon-halogen bond cleavage rates. Electroreduction of CCl4 in RTIL through outer sphere electron transfer would be a promising pathway for its direct conversion to methane.